Association Between Serum β2 -Microglobulin Levels and Prevalent and Incident Physical Frailty in Community-Dwelling Older Women

Abstract

Objectives: To investigate whether higher serum β₂ -microglobulin (B2M) levels, a kidney function marker, are associated with prevalent and incident frailty in community-dwelling older women.

Design: Cross-sectional and longitudinal analyses of a prospective cohort.

Setting: Population-based cohort study in Tokyo, Japan.

Participants: Community-dwelling women aged 75 and older with adequate data for assessing frailty status (N = 1,191) and a subset of participants without baseline frailty but with repeated frailty assessment at 2 and 4 years of follow-up.

Measurements: The primary predictor was B2M level. Outcomes were prevalent and incident frailty during the 4-year follow-up period. Frailty was defined as presence of three of the five Fried criteria: weight loss, exhaustion, weakness, slowness, and low physical activity. Adjusted odds ratios for the main confounders were obtained using logistic regression. Discrete-time Cox proportional hazards models were used to determine the risk of developing frailty.

Results: The study included 241 (20.2%) women with prevalent frailty at baseline and 139 (21.1%) with incident frailty during the 4-year follow-up. On multivariate analysis adjusted for multiple potential confounders, the odds of prevalent frailty were 2.5 times as great with B2M levels of 1.9 to 2.1 mg/L as with levels less than 1.6 mg/L and 2.0 times as great with B2M levels of 2.2 mg/L or more. In the unadjusted model, B2M levels of 1.9 to 2.1 mg/L were associated with a greater incidence of frailty than B2M levels of less than 1.6 mg/L (hazard ratio = 1.72, 95% confidence interval = 1.04-2.86). In the multivariate analysis adjusted for potential confounders, no significant association was noted between the highest B2M quartile and incident frailty.

Conclusion: Higher B2M levels were independently associated with greater frailty at baseline in older adults but only slightly associated with greater risk of incident frailty over 4 years of follow-up.

Keywords: aging; beta-2-microglobulin; epidemiology; frailty; kidney function.